and Kisame isn't a monster? hes literally a shark-ninja hybrid xd and like chojuro (the little swordsman bodyguard) said, kisame is a special case, a bijuu without a tail, and being alive while ninja wars happen doesn't mean he actively fought in them all.
1.Kisame broke out of chakra enhanced wood AFTER getting hit with guy's #1 move, easily overpowered asuma with the tip of his sword without trying,who is a tai expert (with his knife fighting and being able to knock out sound ninja with a single blow when he saved shikamaru) personally i think they'd be matched in raw power.
2.all absorbed by Samehada and if he uses lightning while in the water dome kisame can absorb it thru his skin and kakuzu would be the only one hurt if anything.
3. didn't stop naruto xd but yes that'd be an advantage.
4.He is smarter then Kisame but kisame wasn't a total dunce either, he (with help) switched places with zetsu mid fight, faked his death and hid inside samehada, gathered info on the joint army's plan and successfully got it back to madara and if it wasn't for naruto's unique sensing of evil he probably would have jumped bee at his weakest in the war and captured him.
5.same as 1, i would say they'd be matched at raw power, if kisame doesn't overpower him.